我编写了一个函数，用于绘制（在Base R和ggplot中）KNN分类问题中各种K值的错误分类率。我的问题是，当Base R图显示时，ggplot图不显示。当我从函数中取出ggplot代码时，它可以工作。我不确定我做错了什么。
有人可以指出我做错了吗？
代码：
library(ISLR)
library(ggplot2)
library(class)
data("Weekly")
train <- (Weekly$Year < 2009)
Weekly.train <- Weekly[ train, ]
Weekly.test <- Weekly[ !train, ]
knn.train.x <- scale( as.data.frame(Weekly$Lag2[train]) )
knn.test.x <- scale( as.data.frame(Weekly$Lag2[!train]) )
train.Direction <- Weekly$Direction[train]
set.seed(1234)
#Function for choosing k in knn
misclassknn <- function(train, test,
response.train,
response.test,
Kmax){
K <- 1:Kmax
misclass <- numeric(Kmax)
for( k in K){
knn.pred <- knn(train,test,response.train, k=k)
misclass[k] <- mean(knn.pred!=response.test)
}
# base R
plot(c(1, Kmax), c(0, 1), type = "n",
main = "Misclassification Rate for K Values",
xlab = "K", ylab = "Misclassification Rate")
points(1 : Kmax, misclass, type = "b", pch = 16)
# ggplot
df <- data.frame(1 : Kmax, misclass)
names(df) <- c("misclass", "K")
ggplot(df, aes(x = misclass, y = K)) + geom_line() + ylim(0, 1) +
geom_point() + labs( title = "Misclassification Rate for K Values",
y = "Misclassification Rate", x = "K")
return(list(K = Kmax, misclass = misclass,
Kmin = which.min(misclass)))
}
misclassknn(train = knn.train.x,
test = knn.test.x,
response.train = train.Direction,
response.test = Weekly$Direction[!train],
Kmax = 15)
答案 0 :(得分：3)
我们理所当然地认为绘制R的工作方式。对于ggplot，它实际上返回一个对象，这是一个如何构建绘图的描述。在函数内部，由于范围不同，事物不会像在全局范围内那样显示。基本上你需要手动告诉它通过在ggplot命令周围包装function addverse() {
connection.query('SELECT versetext, book, mp3, id, reference FROM myverses where mp3 = "empty" limit 1',
function (error, results, fields) {
console.log(error);
var scripture = results[0].versetext;
var book = results[0].book;
var reference = results[0].reference.replace(":", " verse ");
console.log(scripture + " " + book.replace("1", "first").replace("2", "second").replace("3", "third") + " " + reference);
var myverse = scripture + " " + book.replace("1", "first").replace("2", "second").replace("3", "third") + " " + reference;
var link = "https://s3.amazonaws.com/myverses/" + book.replace(/ /g, "")+reference.replace(/ /g, "")+".mp3"
function linkit(){
connection.query('update myverses set mp3 = ? where mp3 = "empty" limit 1', [link],
function (error, results, fields) {
console.log(error)
})
}
txtomp3.getMp3(myverse, function(err, binaryStream){
if(err){
console.log(err);
return;
}
function writeit() {
var file = fs.createWriteStream("myverse.mp3");
console.log('recording the verse')
file.write(binaryStream);
file.end();
}
function uploadit () {
console.log('uploading the verse')
AWS.config.update({ accessKeyId: '...', secretAccessKey: '...' });
var s3 = new AWS.S3();
s3.putObject({
Bucket: 'myverses',
Key: book.replace(/ /g, "")+reference.replace(/ /g, "")+".mp3",
Body: myvalue,
ACL: 'public-read'
},function (resp) {
console.log(arguments);
console.log('Successfully uploaded the verse.');
addanother();
});}
writeit();
var myvalue = fs.createReadStream("myverse.mp3");
setTimeout(uploadit, 3000)
});
});
}
或print()来显示绘图，或者你需要将对象作为函数的输出返回，然后从全局调用它范围。基本上你只是强迫它显示对象。
将ggplot对象存储为类似
的常见内容ggplot_build现在，对象p <- ggplot(etc) + geom_etc() + ...
可以根据需要构建到图表中。您可以使用p（或print(p)），也可以在主代码中使用ggplot_build(p)，如果函数返回的话，例如p。